As an alternative to replacing a conduit which has ceased to fulfil its intended purpose satisfactorily, inserting a liner into a conduit often serves to prolong its useful life by preventing escape of fluids carried by the conduit to the surroundings through the walls of the conduit, preventing ingress of fluids in the surroundings through the walls of the conduit into the bore and by giving additional strength to the walls of the conduit. Commonly these linings are inserted to and from access points (such as manholes or excavations) as one continuous section lining extending between the two points of access. However if the distance between two access points is so long that more than one section of lining is required, the lining sections have to be located with their ends at points remote from the access points and this requires remote control. These location problems have been overcome by inserting, under remote control, a deformed liner section into the conduit which when deformed provides adequate clearance between the liner and the conduit to allow free passage of the liner through the conduit to the desired position in the conduit and then reforming the liner section into contact with the conduit walls, by remote control, when the liner section is in the desired position along the length of the conduit.
Further problems are encountered when a liner is expanded in to contact with the walls of the conduit since air or other fluid may become trapped between the liner and the conduit, preventing the liner expanding to its full extent so that its flow capacity is reduced and preventing the liner from supporting the walls of the conduit over their whole area. When the conduit is laid in water-bearing soil, water may be able to penetrate the conduit and cause trouble if the liner does not seal the walls of the conduit completely or if the arc of the lining is deformed.
Another problem occurs if in one location the conduit has broken away and the conduit contents have washed away the surrounding soil. If a standard liner is inserted in such a location, the lack of support for the liner at the broken away location will, when subjected to high expansion forces, allow the liner to balloon out into the void where it will become very thin and probably burst.
Previous lining methods have been limited to lining joints by short lengths of liner (30-100 cms) or to lining conduits from one manhole or excavation to another. The present invention is able to deal with long lengths of liner (say 2-30 meters) lining a conduit over lengths which do not necessarily end at the manhole or excavation. This requires the lining to be transported along the conduit from a manhole or excavation, for a distance of say 5-500 meters.